The present invention relates to a novel process for making aromatic esters. More particularly, this invention relates to the catalytic oxidation of an aromatic aldehyde and an alcohol to form an aromatic ester.
The usual method for the preparation of esters is the reaction of a carboxylic acid and an alcohol with the elimination of water. Thus, to make an ester from an aldehyde by prior art methods is a two-step process. In the first step, the aldehyde is oxidized to a carboxylic acid. The acid is then esterified with an alcohol in the second step. A major disadvantage with these processes, however, is that they require two reactors, one reactor to convert the aldehyde to the acid and one reactor to convert the acid to its corresponding ester.
Esters have also been obtained by the condensation of aldehydes in the presence of alcoholate homogeneous catalysts such as aluminum ethylate. The problem with this prior art process is that it is very difficult to separate the homogeneous catalyst from the solvent, reactants and products.
An advantage of the instant invention is that the catalysts are heterogeneous, and thus, can easily be separated from the reactants and products. Furthermore, the instant process results in very high yields, selectivities and conversions to aromatic esters.